A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

Questions regarding large spheres of plasma undergoing fusion.
Questions about the techniques and practice of observing the night sky.
Questions regarding the closest star to Earth, at the centre of the Solar System.
Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.
Questions regarding an object 'falling around' another object, due to a combination of gravity and momentum.
650 questions
Questions regarding Earth's only natural satellite. For questions about the natural satellites of other planets, use the tag [natural-satellite].
Questions on astronomical objects orbiting a star massive enough to be rounded, not massive enough to cause fusion, and which have cleared its orbit of planetesimals.
Questions regarding systems of large numbers of stars held together by gravity.
Questions related to the physical instruments for astronomical observations.
Questions regarding the Sun and objects orbiting it.
Questions regarding the attractive force which exists between any two bodies of matter.
Questions involving the physics of the universe, especially the nature of astronomical objects, energy fields, and/or regions, rather than their positions or motions in space.
Questions regarding the planet on which humans live; the third planet from the Sun.
475 questions
Questions about the observation of celestial objects by non-professional astronomers.
435 questions
Questions regarding planets that lie outside the Solar System.
Questions about the origin, history, evolution and fate of the Universe.
Questions regarding all of time and space and its contents.
321 questions
Questions regarding electromagnetic radiation in the visible spectrum.
Questions regarding relatively small rocky bodies in an orbit around the Sun.
272 questions
Questions regarding the amount of space between two objects, the units, or measurement thereof.
259 questions
Questions about observations performed in the radio frequency range of the electromagnetic spectrum.
249 questions
The application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.
239 questions
Questions about photography of celestial objects by amateur or professional astronomers. Questions about photography of other objects are off-topic but might be asked on our sister site Photography St…
Questions regarding the Milky Way Galaxy, the galaxy that Earth's solar system is in.
218 questions
Questions on systems to uniquely determine position of a point or other geometric element on a manifold such as Euclidean space.
208 questions
Questions regarding the history of astronomy, including discoveries and scientists.
Questions regarding stars which increase suddenly in energy output due to an explosion which ejected much of its mass.
200 questions
Questions regarding Mars, the fourth planet from the Sun.
199 questions
Questions regarding Jupiter, the 5th and largest planet in the Solar System.
194 questions
Questions regarding the action of or an object rotating along an axis.
190 questions
Questions regarding the 4-dimensional background structure of our universe.
189 questions
Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
Questions on celestial bodies that orbit planets.
182 questions
Questions about the measurement of light waves whereby the wavelength is classified by its position in the electromagnetic spectrum.
180 questions
Analysis of data is a process of inspecting, cleaning, transforming, and modeling data with the goal of discovering useful information, suggesting conclusions, and supporting decision making.
Icy bodies that usually consist of methane, water, and other materials that originate from beyond the jovian planets, and occasionally fall into the inner solar system giving off a massive tail as mat…
174 questions
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